In the printing of an illustration onto a substrate such as paper, there is prepared a printing plate. For a colored illustration, there are a plurality of printing plates. Normally, the number of printing plates is three printing plates, viz., a blue printing plate, a yellow printing plate and a red printing plate. Sometimes there may be used a fourth printing plate referred to as a black printing plate. For example, blue has a wave length range of about three thousand to four thousand angstroms; yellow has a wave length range of about four thousand to five thousand angstroms; and, red has a wave length range of about six thousand to seven thousand angstroms. It is to be understood that there is some overlapping in these ranges, but the approximate ranges are as above described.
The reader is to understand that in the making of a colored illustration there may be more than three printing plates. In some printing shops in the making of a colored illustration there may be as many as nine printing plates so as to be able to print all of the colored dots onto the substrate as required to give a good illustration of the subject matter. With nine printing plates it is possible to have a more complete total range or a more complete spectrum of the colors and a reproduction of the original subject matter.
The preparation of the printing plates for printing the illustration requires the step of making screen separation negatives. Generally, there is prepared a screen separation negative. For a black and white print, there is required one negative or one screen negative. A black and white illustration is monochrome printing or one color. For a colored illustration there is a minimum of two screen separation negatives and for a complete color range from about three thousand to seven thousand angstroms wave length range there is required a minimum of three separation negatives or three screen separation negatives, and in many instances, more than three screen separation negatives are prepared, i.e., as many as nine screen separation negatives, to have a larger tonal range and a larger spectrum of color in the resulting colored illustration.
Again, the reader is to understand that in viewing a colored print the reader is viewing dots of ink on a substrate, and, sometimes the colored dots of ink overlie each other.
In viewing a colored photograph the reader is viewing continuous color and not discrete dots of ink. This invention can be used in the developing of a colored photograph to a desired opaque area and clear area.
From the consideration of cost it is less expensive to make 100,000 colored prints of a subject than to make 100,000 colored photographs of said subject.